Sine wave potentiometer



April 1951 P. ROSENBERG 1 2,549,389

SINE WAVE POTENTIOMETER Filed May 9, 1945 FIG. n FIG.I

/ lllllllumlmi (W W "mum" I F IMVENFOR. PAUL RQJS-ENBERG;

ATTORNEY;

Patented Apr. 17, 1951 UNITED STATES PATENT OFFICE SINE WAVEPOTENTIOMETER Navy Application May 9, 1945, Serial No. 592,795

18 Claims. I

The present invention relates to devices for producing voltages orcurrents which vary sinusoidally and more particularly to a sinusoidalpotentiometer.

The potentiometer according to the present invention provides direct andalternating current Voltages which vary sinusoidally with the angle ofrotation of the shaft of the potentiometer. The invention may havevarious use but has particular application in providing potentialshaving varying amplitudes for deflecting electron beams of cathode raytubes such as disclosed in the copending application of James F.Koehler, Serial Number 594,044, filed May 16, 1945, for Radio EchoDetection System.

An object of the invention is to provide a potentiometer producing adirect current output of sinusoidal form or an alternating current theamplitude of which varies sinusoidally.

Another object of the invention is to provide a potentiometer having aset of brushes and a coil rotatable relatively to each other arranged toprovide a sinusoidal output from the brushes.

These and other objects residing in the arrangement combination andconstruction of the parts will be apparent from the accompanying drawingin which:

Fig. 1 is an elevation of a potentiometer according to the presentinvention,

Fig. 2 is a section on the line IIII of Fig. 1,

Fig. 3 is a partial section on the line III-III of Fig. 2,

Figs. 4, 5, and 7 are partial elevations corresponding to Fig. 1disclosing alternate forms of resistance structures and;

Fig. 6 is a section on the line VIVI of Fig. 5.

Referrin particularly to the drawing, reference character I indicates athin preferably but not necessarily square card of some suitableinsulating material on which is wound a fine resistance wire 2 as shownparticularly in Fig. 1. The wire 2 is preferably enamel coated and it isin closely adjacent turns in physical contact with one another.

The card I is mounted on a disc 3 of insulating material by means ofscrews 4 and 5 and held in spaced relation thereto by spacers 6. Thespacers 6 are in the form of elongated members fiat on the side adjacentthe disc 3 and arched on the side of the card I so as to provide thecard I with a cambered form. The cambered form of the card is ofparticular advantage in that when brushes, hereafter to be described,are relatively moved in contact with the wire 2, the wire 2 is morefirmly held against displacement as a result of the frictional contactof the brushes therewith and the tendency of the brushes tosimultaneously contact several wires 2 at one time is minimized.

The disc 3 is mounted on a shaft I in any suitable manner. As shown, aplate 8 is secured to the shaft 1 and the disc 3 is secured to the plate8 by screws 9. The shaft I is mounted for rotation in a suitable bearingI2 in the housing I3 provided to enclose the operating parts of thepotentiometer. A cylindrical boss I4 is provided at the inner end of theshaft 7 and has telescoped thereonto an insulating sleeve I5. Mounted onthe insulating sleeve I5 are slip rings I6 and I1 spaced from oneanother. The slip ring I6 is connected by a wire I8 to one end of thewire 2 and the slip ring I! is connected by a wire I9 to the other endof the wire 2.

External connection with the slip rings I6 and I? is made through springmetal brushes 2| and 22 a shown particularly in Figs. 2 and 3. ThebrushesZI and 22 are secured to the frame I3 by bolts 23 and 24 and areinsulated therefrom by grommets 25 and 26.

The housing I3 is provided with a cover plate 28 to which are securedsprin arm 29, 39, 3| and 32. The inner ends of these spring arms areprovided with suitable brushes 33, 34, 35 and 36 respectively. Thebrushes 33, 34, 35 and 33 are arranged to lie in a circle which fallswithin the boundaries of the wire 2 on the card I. The enamel or otherinsulation from the wire 2 is buffed or otherwise removed from theconvex surface of the wire 2 on the card I so as to maintain theinsulation between the turns of th wire 2 and to permit electricalcontact between brushes 33, 34, 35 and 36 and the wire 2.

The outer end of the shaft '5 is provided with a gear 40 as a drivingconnection whereby the card I may be rotated relative1y to the brushes34, 35 and 36. It is, however, contemplated that the card I be heldstationary while the brushes 33, 34, 35 and 36 are rotated.

The operation of the invention is as follows: A source of direct currentis connected through the bolts 23 and 24, which may be constituted asbinding posts, to the slip rings I6 and H and thus to the ends of thewire 2. As shown in Fig. 1, the brushes 34 and 36 are across the maximumlength of the wire 2 and therefore the potential between the spring arms30 and 32 is a maximum for this position of the card I with respect tothe brushes 33, 34, 35 and 36. At the same time the length of wirebridged by the brushes 33 and 35 is a minimum and therefore there is aminimum potential between the spring arms 29 and 3|. As the brushes 33,34, 35 and 36 are rotated relatively to the card I, the camber thereofwill cause the contact surface of the brushes to become and remainrounded, as shown particularly in Fig. 2, to thereby insure a minimumcontact of the brushes with the wire 2 of the card I. This feature isimportant for the reason that shorting of turns is minimized. Also theuncertainty as to which turns of wire are contacted by each brush, as inthe case of wide brushes, is avoided. It will be apparent that as thecard I is rotated, the amplitude of the potential across the spring arms29 and 3|, and 39 and 32 will gradually rise and fall respectively andwill take the forms of sine waves.

Figs. 4 through '7 disclose alternative forms of the resistance elementof the invention and in each case, the illustrated resistance elementmay be substituted for the card I in the structures of Figs. 1 and 2,although it is contemplated that differences in materials may requireresistance elements of varying sizes.

In Fig. 4 there is disclosed a flat block38 of carbon or equivalentresistance material, the composition of which may be selected to furnisha resistance of the desired value. Conductors 39 are secured to strips43, respectively, of material of high conductivity such as copper orsilver which are in turn, secured in electrical contact with the block38 to place a potential thereacross.

In Fig. 5 another form of resistance element is disclosedin the form ofa block ii of fibre, or the like, in which thereare recessed apluralityof conducting or resisting bars E2, the edges of which are flush withthe surface of the block 4| as shown particularly in Fig. 6. The ends ofthe bars 42 are connected by conductors 43 to provide a continuousconductor having return bends, which is roughly equivalent to thewindings of the wire 2 on thecard l. The conductor 33 may be resistanceelements if desired.

In Fig. 7 there is disclosed still another form of the invention wherein.a suitable insulating base 4 has the central section thereof coatedwith a, paint or the like having such a conductivity as to provide aresistance element of it. On each side of the central section :5 thereis placed a strip it of silver or equivalent substance of highelectrical conductivity, .each of which is in conducting relation withthe center painted section 4-5. One end of each of the conducting strips46 has connected thereto an electrical conductor 4! for the purpose ofconnecting a voltage across the resistance provided by the centralsection 45.

It will be evident from observation of Figs. 4 through 7 that theresistance elements disclosed thereon are associtaed with thecontactarms'29, 3!], 3| and 32 each having thereon a brush-33, 35 and 33respectively, that a resistance element equivalent to the card l onFigs. 1 and 2 will be provided, and that as the resistance elementshaving potentials thereacross and brushes are rotated relatively to oneanother, a sine wave output will be provided.

While the invention ha been shown as embodying four brushes and two sliprings in the case of a movable resistance element, it will be apparentthat instead there may be four slip rings and four brushes where thebrushes are movable instead :of the resistance element. Also both theresistance element and the brushes may be rotatable at the same time.Also it is within the scope of the invention that there be .more :orless than four brushes. One brush is equally 4 within the scope of theinvention when it is desired to provide only one output having sine wavevoltage and current characteristics. In the claims where the expressioncircular path is employed it is contemplated that a path less than 360is encompassed.

Having thus described my invention, What I desire to secure by LettersPatent and claim is:

l. A potentiometer comprising a resistance element having an archedsurface, said element comprising a wire of uniform resistance uniformlywoundabout an arched form of dielectric material, a contact memberbearing on said resistance element, said arched surface of saidresistance element being arched outwardly in the direction ofsaid'contact member, and means for rotating said contact member in acircular path onsaid'resistance-element whereby the resistance betweensaid contact member and either terminal of said resistance elementvaries sinusoidallyin proportionto the angle through which saidcontactmember is rotated.

.2. Apotentiometer comprising a resistance element having an archedsurface, said resistance element comprising-a wire of uniform resistanceuniformly Wound on a rectangular, arched form of dielectric .material, apair of oppositely disposed bridging contacts bearing on saidresistanceelement, said arched surface of said resistance element beingarched outwardly in the direction ofsaid bridging contacts, and meansfor elatively rotating said resistance element Whereby the resistancebetween said pair of bridging contacts varies sinusoidally as the anglethrough which said resistance element is relatively rotated.

3. A potentiometer comprising aresistanceelement, said elementcomprising .a wire of constant resistance per unit length throughout itsentire length uniformly wound on a rectangular form of dielectricmaterial, said form being slightly arched, first and second pairs ofbridging contacts, said bridging contacts being angularly separatedby.90 degrees and bearing on said resistance element, and means forrelatively rotating said resistance element whereby the resistancesbetween each pair of bridging contacts vary sinusoidally in proportionto the angle through which said resistance element is relativelyrotated.

4. 'A potentiometer comprisingashaftmounted for rotation ina bearing, asubstantially flat resistance element mounted on said shaft, saidresistance element comprising a wire of uniform resistanceuniformly-wound on a rectangular-form of dielectric material, aninsulating sleeve mounted on said shaft, two slip rings mounted on, andsecured-to,-said insulating sleeve, afirst wire connecting-one terminalof said resistance element to .onezof said slip rings, a second'wireconnecting the other terminal of said resistance element to the other ofsaid slip rings, spring brushes contacting said slip rings and beingelectrically joined to terminal posts, and a pair of displaced bridgecontacts bearing on said resistance element.

'5. A poteniometer comprising, .a resistance element formed of aresistance wire wound on an arched rectangular form of insulatingmaterial, first and second .pairsof bridging contacts bearing .on saidresistance element and defining respectivelyfirst and second mutuallyperpendicular lines-and means providing for-relative rotation betweensaid resistance element and said bridgingnontacts, whereby theresistance between contacts of each pair varies sinusoidally inproportion to the rotation angle.

6. A potentiometer comprising, a resistance element formed of aresistance wire uniformly wound upon a rectangular form of insulatingmaterial arched about a first axis, means mounting said resistanceelement for rotation about a second axis perpendicularly intersectingsaid first axis,and means for mounting in fixed space relation to saidsecond axis a number of contacts yieldably bearing on said resistanceelement on the convex side thereof.

7. A potentiometer comprising, a rotatable shaft and an archedresistance element attached thereto, and at least one fixed contactbearing upon the convex surface of said arched resistance element,whereby said contact upon rotation of said shaft and resistance elementtraces a closed path on said convex surface.

8. A potentiometer as in claim '7 wherein said arched resistance elementcomprises, a rectangular form of insulating material uniformly Woundwith resistance wire and slip ring supported on said shaft electricallyconnected to the ends of said resistance wire.

9. A potentiometer comprising, a housing and a shaft journaled forrotation therein, a resistance element amxed to said shaft, a pluralityof pairs of spaced contacts secured to said housing and yieldably bearinagainst said resistance element, said resistance element beingelectrically connected to points on said housing through means enablingfree, continuous rotation of said shaft.

10. A potentiometer as in claim 9 wherein said last-mentioned meanscomprises a sleeve of insulating material affixed to said shaft, sliprings on said insulating sleeve, and means connecting said resistanceelement through said slip rings to terminals on said housing, said lastmeans including brushes secured to said terminals and bearing upon saidslip rings.

11. A potentiometer as in claim 9 wherein said resistance elementcomprise a fiat homogeneous block of resistive material and a spacedpair of conductive strips disposed in electrical contact with saidblock. 3

12. A potentiometer as in claim 9 wherein said resistance elementcomprises a base of insulating material uniformly covered with aresistive film, a pair of spaced conductive strips disposed inconductive contact with said resistive film throughout the lengths ofeach strip.

13. A potentiometer comprising a housing and a shaft journaled therein,a resistance element secured to said shaft within said housing, meansfor insulatedly supporting a slip ring upon said shaft for rotationtherewith, means for conductively coupling said resistance element tosaid slip ring, a terminal post secured to said housing and carrying abrush in yieldable contact with said slip ring, and a contact secured tosaid housing and arranged to bear against said resistance element duringrotation thereof.

14. A potentiometer as in claim 13 wherein said resistance member isarranged to present to said contact a conductive surface havingsubstantially constant resistance as measured between points separatedby a fixed distance.

15. A potentiometer comprising a housing, a shaft journaled in saidhousing and carrying a resistance element formed of resistance wireuniformly wound upon a substantially fiat, rectangular form, aninsulating sleeve mounted upon said shaft for rotation therewith andcarrying a pair electrically separated conductive slip rings connectedto the ends of said resistance wire, a pair of terminal posts secured tosaid housing, a pair of resilient brushe secured to said terminal postsand bearing against said slip rings and a pair of spaced contactssecured to said housing and yieldingly bearing against said resistance'wire and arranged to trace a closed path upon the surface of saidresistance element during rotation thereof.

16. A potentiometer comprising a resistive surface element having thecharacteristic of presenting a substantially constant resistance betweenany two points thereon of fixed separation, means for establishing avoltage gradient on said resistive surface substantially in onedirection, and a contact bearing upon said surface and means forrelatively rotatin said contact and resistive surface.

17. A potentiometer as in claim 16 wherein said resistive surface isarched, said contact being arranged to bear upon the convex surfacethereof.

18. A potentiometer comprising a housing and a shaft journaled forrotation therein, a resistance element affixed to said shaft, at leastone pair of spaced contacts secured to said housing and yieldablybearing against said resistance element, slip rings insulatively mountedon said shaft and electrically connected to said resistance element, andelectrically conductive means mounted on said housing and extending intocontact with said slip rings for electrically connecting said resistanceelement to points on said housing, said slip rings and said lastmentioned electrically conductive means enabling free, continuousrotation of said shaft.

PAUL ROSENBERG.

REFERENCES CITED The following'references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,764,347 Pullwitt June 1'7, 19301,944,329 Langley Jan. 23, 1934 2,034,866 Harvey Mar. 24, 1936 2,042,334Fischer et al May 26, 1936 2,120,100 Illgen June '7, 1938 2,416,363Wellings Feb. 25, 1947

